The invention concerns a method for controlling a transmission of a motor vehicle.
The continuously increasing demands on the functionality of automatic transmissions by shifting quality requirements, the need of more spontaneity the constantly enlarging number of gears to be shifted and the higher economical requirements on automatic transmissions are taken into account in the practice by an adaptive control for automatic transmissions. With such an adaptive transmission control (AGS), the generally pursued end is to adapt the gear selection to the behavior of the individual driver taking into consideration at the same time environmental conditions and concrete driving situations. Thereby among other things, the control comfort should be improved by reducing both the required engagements by the driver and the shifting frequency in sporting driving mode. Besides, the fuel consumption in smooth driving mode is to be lowered, the same as, for example, driving safety increased on even roads.
In order to be able to satisfy, together with an automatic gear selection dependent on driving situation, the requirement of adapting a gear shift to tolerances of the components of shifting elements of the automatic transmission, it has for that purpose been retained in the practice taking into consideration during a gear shift influences of tolerances of the components of shifting elements of the transmission. Here is first established how a transmission or a shifting element of the automatic transmission affected by tolerances of the component parts behaves under minimum and maximum specified tolerance during a gear shift. With the aid of this observation, a shifting cycle is established wherein, with the shifting cycle based on tolerances of components, there are tuned and stored in an electronic control unit pressure curves for a charge pressure abutting on a shifting element during a filling phase and a differential pressure which abuts on the shifting element during a shifting phase and constructively acts upon the filling pressure ultimately producing the engagement of the shifting element.
However, due to the multiplicity of influences that appear in all operating points as result of the tolerances of the components, scatterings of operating parameters of the automatic transmission and other influences, it is not possible with the former steps to derive the right reaction in order to optimize a gear shift, following an evaluated gear shift, that is, to prevent shifting inaccuracies that result from tolerances of components and wear of the shifting elements, the same as temperature influences and scattering fo the operating parameters on the concerned operating point of the automatic transmission.
Therefore, the problem on which this invention is based is to make a method available for control of a transmission of a motor vehicle with which method it is possible to carry out for different influences which impair a suitable gear shift adaptation from which can be derived the respective right reaction for optimizing a subsequent gear shift, especially with regard to a correct clutch filling.
The invention solves this problem with a method according to claim 1.
The invention makes use of the knowledge that an impact or jolt occurring during a bad gear shift results in an acceleration or deceleration of the vehicle and thus necessarily goes along with a change of a speed signal of the output train. According to the invention, especially the output speed signal is relatively uniform and very closely resembles a straight line, for example, in a pull upshift. Likewise, up to the actual speed jump, this applies to the turbine speed. Divergences from the straight line indicate irregularities in the output speed curve which are to be traced back to an engagement impact.
In the inventive method, a speed signal of the output train is determined with precalculatable time curve and for adjustment of a nominal filling of the shifting elements, an interference signal is applied to the shifting element observed at the moment, a divergence from the nominal filling of the shifting element is determined in case of an Intolerable divergence of the speed signal of the output train from its precalculated curve. This information is processed for control of the shifting elements.
Irregularities of the speed signal of the output train, which can be detected represent events that detract from the shifting quality, such as brief acceleration in creases or breakdowns, due to pressure pulses in clutches or interruptions of frictional engagement, a shifting jolt resulting from too long a rapid filling time of an engaging shifting element, a brief deceleration of the vehicle due to strong overlapping before the grinding phase of the shifting elements that take part in an overlapping gear shift, or a shifting jolt at the end of a gear shift resulting from too early starting of the closing ramp of an engaging shifting element.
From the unexpected changes of the speed curve can be detected not only the presence of an impact indicative of a bad shifting quality but also the nature and strength of an impact, it being possible to use this information for an adaptation control. With the inventive method not only broadening of already existing adaptations are possible, but there can also be newly defined numerous adaptations, such as a rapid filling adaptation, a charge pressure adaptation, an overlapping adaptation, synchronous adaptation, supporting pressure adaptation for coasting downshifts, engine engagement adaptations and different adaptations of regulated lock-up clutch.
In each of these different adaptations, the inventive method displays considerable advantages. Thus it is possible to apply rapid filling time adaptation and charge pressure adaptation to all gear shifts and the clutch fillings for each individual transmission can be optimally adjusted. All tuning works are eliminated relative to rapid filling and filling equalization. Costly marginal sampling analyses in this connection are superfluous and the cost in cold tests also can be significantly reduced. Negative consequences on the shifting curve, due to incorrect clutch filling, can be prevented by means of the inventive method.
For example, observing the application to an overlapping adaptation, it is possible with the inventive method to optimally adjust the overlapping phase of a pull upshift for each transmission separately, that is, the moment of start of the engaging clutch based on the disengaging clutch whereas formerly one adjustment applied to all transmissions so that all scatterings in the tolerance chain had to be covered.
Likewise the use of the inventive method in an engine engagement adaptation is very advantageous where the intensity of the engine engagement for upshifts in the pull operation is self-optimizingly adjusted. A tuning of the engine engagement is no longer needed here, since its intensity can be adapted so that the acceleration behavior of the vehicle is optimal during the gear shift.
The start of the closing ramp also can be self-optimizingly designed with the inventive method wherein corresponding tuning works are eliminated, since the closing ramp is individually adjusted for each transmission.
An extensive tuning of a transmission operated with the inventive method is no longer required, since it is possible by evaluating the divergences of the speed signal from its precalculated curve, to carry out a compensation of tolerances of components of the shifting elements of the transmission for different shifting strategies or kinds of shifting, whereby tolerances of components determined by the manufacturing process and also a wear of components occurring during the operation of the transmission or the shifting element thereof can be quickly compensated.
At the same time, the inventive method makes a very accurate adaptation of the control of the shifting elements possible, since not only is there detected an impact on the output speed signal and with shifted gear on the turbine speed signal, which impact can be felt as disturbing by the occupants of the vehicle but even impacts on the speed signal so small that a driver cannot perceive them can also be already detected.